经研究,白蜡吉丁肿腿蜂Sclerodermus pupariae Yang et Yao与哈氏肿腿蜂Sclerodermus harmandi (Buysson)均可寄生锈色粒肩天牛Apriona swainsoni(Hope)的低龄幼虫,可用于该害虫的生物防治。为了探讨其学习行为,采用Y-型嗅觉仪、培养皿...经研究,白蜡吉丁肿腿蜂Sclerodermus pupariae Yang et Yao与哈氏肿腿蜂Sclerodermus harmandi (Buysson)均可寄生锈色粒肩天牛Apriona swainsoni(Hope)的低龄幼虫,可用于该害虫的生物防治。为了探讨其学习行为,采用Y-型嗅觉仪、培养皿两种方法,测定了锈色粒肩天牛虫粪及其寄主植物——国槐韧皮部的气味刺激对交配后的白蜡吉丁肿腿蜂和哈氏肿腿蜂的雌蜂嗅觉记忆的影响。结果表明,这两种肿腿蜂在羽化后经过对上述两种气味源48h接触后,有学习经历的雌蜂对两种气味源的选择性比没有学习经历的雌蜂对气味源的选择性相比显著提高。在对气味源的搜寻判断上,有学习经历的雌蜂所用时间显著少于没有学习经历的雌蜂。培养皿试验表明,有学习经历的雌蜂对锈色粒肩天牛虫粪及国槐树枝韧皮部水提物或正丁烷提取物的趋向率要高于没有学习经历的雌蜂,但二者差异不显著。两种寄生蜂的嗅觉记忆具有一定的稳定性和持久性,当其脱离学习环境一定时间后,对气味源仍有较强的趋向性。展开更多
We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that whe...We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that when GS<60 nm,the superelastic stress-strain hysteresis loop area(H)of the polycrystal decreases rapidly with GS and tends to vanish as GS approaches 10 nanometers.At the same time,the temperature dependence of the transition stress also decreases with GS and eventually approaches zero,leading to a wide superelastic temperature window and breakdown of the Clausius-Claperyon relationship.Rate dependence of the stress-strain responses is significantly reduced and the cyclic stability of the material is improved by the nanocrystallization.It is proposed that the emergence of such significant changes in the behavior of the material with GS reduction originate from the large increase in the area-to-volume ratios of the nanometer-thick interfaces(grain boundary and Austenite-Martensite(A-M)interface)in the polycrystal.In particular,with GS reduction,interfacial energy terms will gradually become dominant over the bulk energy of the crystallite,eventually bring fundamental changes in the phase transition responses of the material.Modelling strategy leading to the establishment of quantitative relationships among GS,grain boundary,A-M interfaces and the macroscopic responses of the material are outlined.展开更多
The as-cast ingot of equiatomic nickel-titanium shape memory alloy （SMA） was prepared via vacuum consumable arc melting. Differential scanning calorimetry （DSC）, X-ray diffraction （XRD） analysis, energy dispersi...The as-cast ingot of equiatomic nickel-titanium shape memory alloy （SMA） was prepared via vacuum consumable arc melting. Differential scanning calorimetry （DSC）, X-ray diffraction （XRD） analysis, energy dispersive X-ray （EDX） measurement and microanalysis were adopted in order to understand the microstructure evolution and deformation behavior of the as-cast NiTi SMA under compression at various strain rates and temperatures. The microstructures of as-cast NiTi SMA composed of dendritic grains and equiaxed grains are inhomogeneous and show segregation. The as-cast NiTi SMA consists of B19′ martensite, B2 austenite and Ti2Ni phase simultaneously at room temperature. The as-cast NiTi SMA is sensitive to strain rate under compression at high temperature, at which NiTi SMA is characterized by dynamic recrystallization at strain rates of 0.1 and 0.01 s-1, but by dynamic recovery at strain rate of 0.001s-1. The strain rates have little influence on the true stress—strain curves as well as microstructure of NiTi SMA at room temperature and -100 °C.展开更多
Laser additive manufacturing (AM) of lattice structures with light weight, excellent impact resistance, and energy absorption performance is receiving considerable attention in aerospace, transportation, and mechanica...Laser additive manufacturing (AM) of lattice structures with light weight, excellent impact resistance, and energy absorption performance is receiving considerable attention in aerospace, transportation, and mechanical equipment application fields. In this study, we designed four gradient lattice structures (GLSs) using the topology optimization method, including the unidirectional GLS, the bi-directional increasing GLS, the bi-directional decreasing GLS and the none-GLS. All GLSs were manufactureed by laser powder bed fusion (LPBF). The uniaxial compression tests and finite element analysis were conducted to investigate the influence of gradient distribution features on deformation modes and energy absorption performance of GLSs. The results showed that, compared with the 45° shear fracture characteristic of the none-GLS, the unidirectional GLS, the bi-directional increasing GLS and the bi-directional decreasing GLS had the characteristics of the layer-by-layer fracture, showing considerably improved energy absorption capacity. The bi-directional increasing GLS showed a unique combination of shear fracture and layer-by-layer fracture, having the optimal energy absorption performance with energy absorption and specific energy absorption of 235.6 J and 9.5 J g-1 at 0.5 strain, respectively. Combined with the shape memory effect of NiTi alloy, multiple compression-heat recovery experiments were carried out to verify the shape memory function of LPBF-processed NiTi GLSs. These findings have potential value for the future design of GLSs and the realization of shape memory function of NiTi components through laser AM.展开更多
文摘经研究,白蜡吉丁肿腿蜂Sclerodermus pupariae Yang et Yao与哈氏肿腿蜂Sclerodermus harmandi (Buysson)均可寄生锈色粒肩天牛Apriona swainsoni(Hope)的低龄幼虫,可用于该害虫的生物防治。为了探讨其学习行为,采用Y-型嗅觉仪、培养皿两种方法,测定了锈色粒肩天牛虫粪及其寄主植物——国槐韧皮部的气味刺激对交配后的白蜡吉丁肿腿蜂和哈氏肿腿蜂的雌蜂嗅觉记忆的影响。结果表明,这两种肿腿蜂在羽化后经过对上述两种气味源48h接触后,有学习经历的雌蜂对两种气味源的选择性比没有学习经历的雌蜂对气味源的选择性相比显著提高。在对气味源的搜寻判断上,有学习经历的雌蜂所用时间显著少于没有学习经历的雌蜂。培养皿试验表明,有学习经历的雌蜂对锈色粒肩天牛虫粪及国槐树枝韧皮部水提物或正丁烷提取物的趋向率要高于没有学习经历的雌蜂,但二者差异不显著。两种寄生蜂的嗅觉记忆具有一定的稳定性和持久性,当其脱离学习环境一定时间后,对气味源仍有较强的趋向性。
基金supported by the Hong Kong Research Grant Council(RGC)(Grant No.619113)the National Natural Science Foundation of China(Grant No.11128204)the State Key Lab of Water Resources and Hydropower Engineering of WHU,China
文摘We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that when GS<60 nm,the superelastic stress-strain hysteresis loop area(H)of the polycrystal decreases rapidly with GS and tends to vanish as GS approaches 10 nanometers.At the same time,the temperature dependence of the transition stress also decreases with GS and eventually approaches zero,leading to a wide superelastic temperature window and breakdown of the Clausius-Claperyon relationship.Rate dependence of the stress-strain responses is significantly reduced and the cyclic stability of the material is improved by the nanocrystallization.It is proposed that the emergence of such significant changes in the behavior of the material with GS reduction originate from the large increase in the area-to-volume ratios of the nanometer-thick interfaces(grain boundary and Austenite-Martensite(A-M)interface)in the polycrystal.In particular,with GS reduction,interfacial energy terms will gradually become dominant over the bulk energy of the crystallite,eventually bring fundamental changes in the phase transition responses of the material.Modelling strategy leading to the establishment of quantitative relationships among GS,grain boundary,A-M interfaces and the macroscopic responses of the material are outlined.
基金Project (51071056) supported by the National Natural Science Foundation of ChinaProject (HEUCFR1132) supported by the Fundamental Research Funds for the Central Universities of China
文摘The as-cast ingot of equiatomic nickel-titanium shape memory alloy （SMA） was prepared via vacuum consumable arc melting. Differential scanning calorimetry （DSC）, X-ray diffraction （XRD） analysis, energy dispersive X-ray （EDX） measurement and microanalysis were adopted in order to understand the microstructure evolution and deformation behavior of the as-cast NiTi SMA under compression at various strain rates and temperatures. The microstructures of as-cast NiTi SMA composed of dendritic grains and equiaxed grains are inhomogeneous and show segregation. The as-cast NiTi SMA consists of B19′ martensite, B2 austenite and Ti2Ni phase simultaneously at room temperature. The as-cast NiTi SMA is sensitive to strain rate under compression at high temperature, at which NiTi SMA is characterized by dynamic recrystallization at strain rates of 0.1 and 0.01 s-1, but by dynamic recovery at strain rate of 0.001s-1. The strain rates have little influence on the true stress—strain curves as well as microstructure of NiTi SMA at room temperature and -100 °C.
基金supported by the financial support from the National Natural Science Foundation of China(Nos.51735005 and U1930207)the Basic Strengthening Program(No.2019-JCJQ-JJ-331)+1 种基金National Natural Science Founda-tion of China for Creative Research Groups(No.51921003)the 15th Batch of‘Six Talents Peaks’Innovative Talents Team Program(No.TD-GDZB-001).
文摘Laser additive manufacturing (AM) of lattice structures with light weight, excellent impact resistance, and energy absorption performance is receiving considerable attention in aerospace, transportation, and mechanical equipment application fields. In this study, we designed four gradient lattice structures (GLSs) using the topology optimization method, including the unidirectional GLS, the bi-directional increasing GLS, the bi-directional decreasing GLS and the none-GLS. All GLSs were manufactureed by laser powder bed fusion (LPBF). The uniaxial compression tests and finite element analysis were conducted to investigate the influence of gradient distribution features on deformation modes and energy absorption performance of GLSs. The results showed that, compared with the 45° shear fracture characteristic of the none-GLS, the unidirectional GLS, the bi-directional increasing GLS and the bi-directional decreasing GLS had the characteristics of the layer-by-layer fracture, showing considerably improved energy absorption capacity. The bi-directional increasing GLS showed a unique combination of shear fracture and layer-by-layer fracture, having the optimal energy absorption performance with energy absorption and specific energy absorption of 235.6 J and 9.5 J g-1 at 0.5 strain, respectively. Combined with the shape memory effect of NiTi alloy, multiple compression-heat recovery experiments were carried out to verify the shape memory function of LPBF-processed NiTi GLSs. These findings have potential value for the future design of GLSs and the realization of shape memory function of NiTi components through laser AM.
